The invention pertains to a television receiver. More specifically, the present invention pertains to a television receiver with a multipicture display.
In a television receiver with multipicture display a single video signal can be reproduced simultaneously in two or more subareas, or two or more different video signals can each be reproduced in associated subareas. Each of the subareas can display either a reduced-size picture or a part of the picture supplied by a video-signal source. A digital signal-processing circuit converts the signals from the video-signal source to picture data consisting of luminance and color data for each picture element. A random-access memory (RAM) holds the picture data of the entire screen. A control unit controls the writing of the picture data into an area of the RAM depending on the number of video signals to be reproduced and the line-by-line readout, with only selected lines being transferred from the video-signal source into the associated memory area. A digital-to-analg converted which is furnished with the picture data read from the RAM delivers the analog red, green, and blue signals.
A television receiver of this kind is described in a printed publication by Intermetall Semiconductors ITT, "VMC Video Memory Controller", August 1985.
That television receiver circuit uses random-access memories (RAMs). For the multipicture display, the screen is divided into up to nine equal-sized subareas which each contain a part of a picture of normal size or a complete picture of reduced size. In that mode, successively produced "snapshots" of up to nine different video signals can be displayed simultaneously. The switching of the video signals takes place manually.
Offenlegungsschrift DE No. 24 13 839 A1 describes a circuit for a television receiver with a facility for simultaneously reproducing two or more programs. In a part of the picture of the directly received main program, the secondary program, received with a single switchable tuner, is stored in a memory with a reduced number of lines and is called up line by line when the electron beam of the picture tube sweeps across the predetermined part of the picture. The disadvantage of this method lies in horizontal grating-like interference in the main picture which results from the fact that lines of the main picture are missing at regular intervals when the tuner has been switched to the secondary program, and which can only be incompletely compensated.